EP2413538B1 - Prevention of transmission loops in a redundant ring network - Google Patents

Description

The invention relates to redundant communication in a communication system, in particular to redundant communication in a communication system having a plurality of communication networks. A method according to the preamble of claim 1 is made US 2006/215544 A1 known.

In US 2009/016384 A1 A method is described for distributing synchronized status messages within a resilient packet ring network, in which data packets with timing information are generated by encoding Synchronization Status Messaging messages into OAM data packets in accordance with IEEE 802.3ah. Information specifying a transmission direction of a respective message is also encoded in the OAM data packets. For data packets with synchronization status messaging information, Resilient Packet Ring protections are disabled. These data packets are transmitted to adjacent network nodes in accordance with the information about the transmission direction.

A network is understood here in particular as an association of several network devices that can communicate with each other wirelessly or via network cables. In a communication system having a plurality of communication networks, the communication networks are connected to each other via so-called coupling nodes. The coupling nodes serve to allow data to be transferred from a first communication network to a second and vice versa. A communications network-spanning communication is thus possible in such a communication system.

A redundant communication in such a communication system is advantageous because interruptions of the communication path do not automatically mean that the communication can not take place. When using a second communication path this can be used as an alternative to the first Communication path, if the first communication is interrupted. This type of communication is mainly used in automation networks, where automation data, which are important for a production process, are used.

Such a redundant communication can take place, for example, in that a signal, which is to be transmitted from a first network device of a first communication network to a second network device of a second communication network, to a coupling node, which connects the first communication network to the second communication network, both to a Network device of the first communication network as well as to another coupling node in second communication network is output. The signal is thus transmitted both in the first and in the second communication network. The signal transmitted further via the first communication network is then transmitted to a further coupling node to a further coupling node of the second communication network. In this way, two different network paths arise from the first network device of the first network to the second network device of the second communication network.

The invention is the object of the invention to provide an improved method for redundant communication in a communication system. It is another object of the present invention to provide an improved coupling node, an improved computer-readable storage medium for such a coupling node, and an improved communication system having such a coupling node.

The objects underlying the invention are each achieved with the features of the independent claims. Embodiments of the invention are given in the dependent claims.

According to the invention, a method for redundant communication in a communication system is provided. The communication system comprises several communication networks. The communication networks are connected to each other via at least one coupling node. The communication networks include multiple network devices.

Within the communication system, data is transmitted from a first network device of the first communication network to a second network device of the second communication network via at least one coupling node and / or from the first network device to a third network device of the first communication network. The transmission from the first to the second network device and / or the transmission from first to third network device via at least two redundant transmission paths. Two redundant transmission paths mean here that two different paths from the first to the second and / or from the first to the third network device for the transmission of the data are used within the communication network. If one of the two transmission paths should be faulty or interrupted, the data reaches its destination via the other transmission path.

Due to an information predefined before the transmission, a retransmission of the data from the second to the first communication network during a transmission from the first to the second network device is prevented. The predefined information consists of a first part and a second part. The data comprises the first part of the predefined information and the coupling node comprises the second part of the predefined information.

Such a prevention of the retransmission of the data from the second to the first communication network is advantageous because it avoids the unnecessary transfer of data back into the first communication network. Since the destination of the data lies in the second communication network, it is advantageous to prevent a retransmission of the data into the first communication network. This avoids that data in the first network circling, without this forms a redundant transmission path to the second network device. The prevention is thus advantageous to prevent unnecessary traffic in the first network.

Preventing retransmission also reduces the maximum possible skew between a frame of data and its duplicate transmitted over the second redundant transmission path. Such duplicates, which have been registered twice at a coupling node or at a network device, are filtered with a duplicate filter list. By reducing the maximum possible Maturity differences can reliably filter duplicates with a smaller duplicate filter list.

This is particularly advantageous in automation systems that include multiple automation networks.

An automation network may e.g. be designed as an industrial automation network. Such industrial automation networks may e.g. for the control and / or regulation of industrial installations (for example production plants, conveyor systems, etc.), machines and / or devices, which are designed and / or provided. In particular, automation networks or industrial automation networks real-time communication protocols (eg Profinet, Profibus, Real-Time Ethernet) for communication at least between the components involved in the control and / or regulatory tasks (eg between the control units and the systems to be controlled and / or Machines). The secure transmission of data via storage media is also covered.

Furthermore, in addition to a real-time communication protocol, at least one further communication protocol (which, for example, need not be real-time capable) may also be provided in the automation network or industrial automation network, e.g. for monitoring, setting up, reprogramming or / or reparameterizing one or more control units in the automation network.

An automation network may e.g. Wired communication components and / or wireless communication components include. In addition, an automation network may include at least one automation device.

An automation device can be, for example, a computer, PC and / or controller with control tasks or control capabilities. In particular, an automation device For example, be an industrial automation device, for example, designed, equipped and / or provided specifically for controlling and / or regulating industrial plants. In particular, such automation devices or industrial automation devices can be real-time capable, ie enable real-time control or regulation. For this purpose, the automation device or the industrial automation device, for example, comprise a real-time operating system and / or at least support, inter alia, a real-time communication protocol for communication (eg Profinet, Profibus, Real-Time Ethernet).

An automation network includes multiple sensors and actuators. The actuators and sensors are controlled by at least one control device. The actuators, the sensors and the at least one control device exchange data with each other. An automation protocol is used for data exchange. The at least one controller controls the actuators, the sensors and the data exchange so that a machining process takes place in which e.g. a product is produced.

An industrial automation device may e.g. a programmable logic controller, a module or part of a programmable logic controller, be integrated in a computer or PC programmable logic controller and corresponding field devices, sensors and / or actuators, input and / or output devices or the like for connection to a programmable logic controller or include such.

As an automation protocol in the context of the present invention, any type of protocol is provided, which is provided for communication with automation devices according to the present description, suitable and / or set up. Such automation protocols can be, for example, the professional bus protocol (eg according to IEC 61158 / EN50170), a Profi-Bus-DP protocol, a Profi-Bus-PA protocol, a Profi-Net protocol, a Profi-Net-I0 protocol, a protocol according to AS-Interface, a protocol according to IO Link, a KNX protocol, a multipoint interface (MPI) protocol, a point-to-point (PtP) protocol, a protocol according to the specifications of S7 communication (which is provided and set up, for example, for the communication of programmable logic controllers from Siemens) or an industrial Ethernet protocol or real-time Ethernt protocol or other specific protocols for communication with automation devices. As an automation protocol in the sense of the present description, any combination of the aforementioned protocols may be provided.

According to embodiments of the invention, the first part of the predefined information is read by the at least one coupling node. The coupling node then knows both parts of the predefined information. The first part was read out of the data by the coupling node and the second part is located in the coupling node, for example on a digital storage medium, and can also be read by the coupling node.

The first part of the predefined information according to embodiments of the invention is a source address of the data. The source address of the data is the address of the network device that sent the data. This can be for example a medium access control (MAC) address. The source address uniquely identifies the network device.

In this case, the second part of the predefined information is in a database of the coupling node. Each entry of the database includes a network device address and at least one forward control (FWC) bit. With the at least one FWC bit is adjustable that data for example only from the first to the second network, but not from the second to the first network may be sent. The at least one FWC bit determines via which ports the coupling node forwards the received data.

When data having a particular source address is received by the coupling node, the coupling node in the database determines the second predefined information by comparing the source address with the database entries. The second predefined information may be, for example, the at least one FWC bit that determines whether the received data is forwarded to the first and / or second network.

According to embodiments of the invention, the coupling node comprises a plurality of ports. Data can be received and sent via each of the ports. The second part of the predefined information is in a database. The database contains several entries.

First, data is received at a first port. From this data, the first part of the predefined information is read out. The second part of the predefined information is determined by comparing the database entries with the first part of the predefined information. At least one second port for forwarding the data is determined from the second part of the predefined information if the second part of the predefined information comprises at least one second port. The data is then forwarded via the at least one second port if the second part of the present information comprises at least one second port. If the second part of the predefined information does not include a second port, forwarding of the data is prevented.

The coupling node thus determines the second part of the predefined information with the aid of the first part of the predefined information Information. The second part of the predefined information indicates whether and if so, how many and which ports should be used to forward the data. Thus, the forwarding direction of the data can be defined by the first and first second part of the predefined information. For example, the first part and the second part of the predefined information may specify that the data is forwarded only over the port that is connected to the first network. This prevents transmission of data to the second network. The same method can also be used to prevent transmission of data from the second to the first communication network.

According to embodiments of the invention, the coupling node comprises a plurality of ports. Data can be received and sent via each of the ports. The second part of the predefined information consists of a database. The database comprises a plurality of entries, each entry for each of the ports comprising no or at least one associated send port.

The first part of the predefined information comprises a data destination. This can be, for example, a multicast or unicast address of the data. The first part of the predefined information thus defines the network device to which the data is to be transmitted.

At the coupling node, the data is first received at a first port. The coupling node then reads the data destination and registers the first port as a receive port. The database is then searched for the database entry that matches the data destination and the first port. Each database entry also includes no or at least one send port. The respective send port is thus determined by the first port and the data destination. It is also possible that for a first port and a certain data destination no send port is defined. In this case, the data will not be forwarded.

From the database, the at least one send port associated with the first port is read out if the database entry comprises at least one send port. The data is forwarded via the at least one read out transmission port if the database entry comprises at least one transmission port. If the database entry does not include a send port, the data is prevented from being forwarded.

In other words, the coupling node determines from the data destination and the reception port whether and via which or which ports the data should be forwarded.

According to embodiments of the invention, each database entry and the data destination is characterized by a multicast address or a unicast address.

According to embodiments of the invention, the communication system is an automation system. The data in this case is automation data. Such an automation system is particularly advantageous because unnecessary data transfers in the first network are prevented. Thus, possible delays in transmission of other data in the first communication network are prevented. This ensures a smooth production process with the aid of the automation system.

In a further aspect, the invention relates to a coupling node with multiple ports. The ports are configured to connect at least a first communication network of a communication system to a second communication network of the communication system. Each port is connected to a communication network. For example, two ports of the coupling node to a first communication network and two ports of the coupling node to a second Be connected communication network. Thus, the coupling node may forward data within the first communication network or within the second communication network. A forwarding of data from the first communication network to the second communication network and vice versa can take place.

Data can be received from the first and the second communication network via the ports and sent out to the first and the second communication network. The coupling node comprises means for reading out a first part of predefined information from the data. The coupling node further comprises memory means and read-out means for storing and reading a second part of the predefined information. Preferably, the second part of the predefined information is stored on a digital storage medium in the coupling node.

In addition, the coupling node comprises prevention means. The preventing means are adapted to prevent transmission of received data originally originating in the first communication network and received at the coupling node from the second communication network back into the first communication network, depending on the predefined information.

In still another aspect, the invention relates to a computer readable storage medium having instructions that when executed in a coupling node according to embodiments of the invention in a communication system cause the coupling node to perform the following method.

First, data is received via a first port. The first port is registered as a receive port. A first part of a predefined information is read from the received data. A second part of the predefined information is read from the storage means of the coupling node. A transmission of the received data originally originating from the first communication network and received at the coupling node by the second communication network back into the first communication network is prevented on the basis of the predefined information.

In yet another aspect, the invention relates to a communication system having at least one coupling node according to embodiments of the invention. The communication system comprises at least a first and a second communication network. The at least one coupling node comprises a plurality of ports, wherein the coupling node connects via the ports at least the first communication network with the second communication network of the communication system.

Figur 1

eine schematische Darstellung eines Eintrags in einer Datenbank des Kopplungsknotens mit FWC-Bits;

Figur 2

eine schematische Darstellung eines Kopplungsknotens mit vier Ports, über die Daten empfangen und gesendet werden können, wobei die Weiterleitung von Daten an bestimmte Ports durch bestimmte Forward-Controlling-Bits verhindert wird;

Figur 3

eine schematische Darstellung eines Eintrags in einer Datenbank im Kopplungsknoten, bei dem einem ersten Port ein zu dem ersten Port zugehöriger Empfangsport zugeordnet wird;

Figur 4

eine schematische Darstellung eines Kommunikations-systems mit zwei Kommunikationsnetzwerken, die über Kopplungsknoten miteinander verbunden sind, wobei die Datenübertragung vom zweiten zum ersten Netzwerk verhindert wird.

Figur 5

eine schematische Darstellung eines Kommunikations-systems mit zwei Kommunikationsnetzwerken, die über Kopplungsknoten miteinander verbunden sind, wobei die Datenübermittlung vom ersten zum zweiten Netzwerk verhindert wird;

Figur 6

ein Kommunikationssystem mit zwei Kommunikations-netzwerken, die über Kopplungsknoten miteinander verbunden sind, wobei ein Kommunikationsnetzwerk girlandenförmig aufgebaut und ein Kommunikations-netzwerk ringförmig aufgebaut ist;

Figur 7

ein Kommunikationssystem mit zwei Kommunikations-netzwerken mit redundanter Kommunikation eines Senders in dem girlandenförmigen Netzwerk;

Figur 8

eine schematische Darstellung eines Kommunikations-systems mit zwei Kommunikationsnetzwerken mit einem Datensender im ringförmigen Netzwerk und einer redundanten Kommunikation; und

Figur 9

ein Blockdiagramm eines Kopplungsknotens.

In the following, embodiments of the invention will be explained in more detail with reference to the drawings. Show it:

FIG. 1

a schematic representation of an entry in a database of the coupling node with FWC bits;

FIG. 2

a schematic representation of a coupling node with four ports over which data can be received and sent, the forwarding of data to certain ports is prevented by certain forward controlling bits;

FIG. 3

a schematic representation of an entry in a database in the coupling node, in which a first port associated with the first port receiving port is assigned;

FIG. 4

a schematic representation of a communication system with two communication networks, which are interconnected via coupling nodes, the data transmission from the second to the first network is prevented.

FIG. 5

a schematic representation of a communication system with two communication networks, which are interconnected via coupling nodes, wherein the data transmission is prevented from the first to the second network;

FIG. 6

a communication system having two communication networks connected to each other via coupling nodes, wherein a communication network is garland-shaped and a communication network is ring-shaped;

FIG. 7

a communication system having two communication networks with redundant communication of a transmitter in the garland-shaped network;

FIG. 8

a schematic representation of a communication system with two communication networks with a data transmitter in the annular network and a redundant communication; and

FIG. 9

a block diagram of a coupling node.

Elements of the following figures that correspond to each other are identified by the same reference numerals.

FIG. 1 is a schematic representation of an entry 100 in a database of a coupling node. The coupling node connects two communication networks (not shown here). Each database entry of this database is compared with a first part of a predefined information of data to be transmitted. The first part of the predefined information according to embodiments of the invention is the source address of the data. The source address of the data is the address of the network device that sent the data. The source address of the data may be, for example, a media access Control (MAC) source address. The MAC source address may also be referred to as MAC-SA. This abbreviation stands for MAC source address. The database entry 100 comprises 64 bits, with the numbering running from 0 to 63. A MAC-SA 102 is stored in bits 16-63 of the database entry 100. In addition, database entry 100 includes two forward control (FWC) bits 104. The FWC bits are bits 14 and 15 of database entry 100. Also, more FWC bits or just one FWC bit may be used. The FWC bits form a second part of the predefined information.

Now, when data is received at the coupling node, the coupling node reads out the first predefined information from the data. The first predefined information is the MAC-SA of the data. Then, the coupling node compares this MAC-SA of the data with the entries in the database. If the MAC-SA of the data matches the MAC-SA 102 of an entry in the database, the coupling node reads out the FWC bits 104 of the database entry and forwards the data using the FWC bits.

FIG. 2 includes four schematic representations of a coupling node 200 and illustrates the routing of data when the second predefined information has been read out. Depending on the read second predefined information, the FWC bits, the data is forwarded differently. The coupling node 200 comprises four ports 202, 204, 206, 208.

In Part A of FIG. 2 the coupling node 200 has read out the FWC bits 0: 0. In this case, the coupling node 200 forwards the data to each of its four ports 202, 204, 206, 208. In this case, the data is re-issued via each port.

The coupling node 200 may be located, for example, in a first communication network. Over port 204 can Data is received from a second automation network. Via port 202 data can be output to the second communication network. The ports 206 and 208 are each for receiving and transmitting data from the first and the first communication network.

Part B of FIG. 2 is a schematic view of a coupling node 200 as in part A. The difference to part A is that the FWC bits 0: 1 have been read from the database. The FWC bits 0: 1 cause the coupling node 200 to transmit no data over port 202. Thus, a transmission of the data to the second communication network is prevented.

Part C is a schematic view of a coupling node 200 as seen from parts A and B. Here now, the coupling node has read out the FWC bits 1: 0. These FWC bits cause the coupling nodes to not output data received over the port 204 from the second network to the first network. This may be the case, for example, for data that should not be transmitted to the first communication network.

Part D is a schematic representation of a coupling node 200 as in parts A-C, with the difference that the coupling node 200 has read out the FWC bits 1: 1. In such a case, both the data is prevented from being transmitted from the first to the second network and from the second to the first network. Only one transfer from port 206 to port 208 or vice versa is possible. Thus, both the transmission of data from the first to the second network and vice versa is prevented.

This method may also be referred to as source address dependent routing of the data.

FIG. 3 Figure 3 is a schematic view of a database entry 300 in a coupling node in a communication system. The database entry 300, in contrast to the database entry, comprises the FIG. 1 a destination address (MAC-DA) 302. The MAC-DA 300 has the same format as the MAC-SA FIG. 1 , The destination address 302 denotes a data destination. The MAC-DA 302 corresponds to the MAC address of a network device. In addition, the database entry 300 in bits 0 through 15 includes four entries 304, 306, 308, 310 in which a send port is specified for the destination address 302 for each potential receive port of the link node. The entries 304-310 may therefore also be referred to as commit bits.

The database entry 300 thus determines for data with the destination address 302 via which port the data is to be sent out when they are received at a specific port. For example, commit bits 304 specify the associated transmit port for receiving the data at a first port, while commit bits 306 specify the transmit port for receiving the data at a second receive port. The same applies to designation bits 308 and 310 for a third and a fourth reception port. This means that one or more send ports are defined for each potential receive port. The commit bits 304-310 may also specify for a receive port that the data is no longer transmitted. In this case, database entry 300 for data destination 302 does not include an associated send port with the corresponding receive port.

This method can also be referred to as destination-address-dependent forwarding of the data.

FIG. 4 16 is a schematic view of a communication system 400 having a first communication network 402 and a second communication network 404. The first communication network 402 is connected to the second communication network 404 by means of four coupling nodes 408, 410, 412, 414 connected. The coupling nodes 408 and 410 form a connection of the first communication network 402 with the second communication network 404 at a first location and the coupling nodes 412 and 414 form the connection of the first communication network 402 with the second communication network 404 at a second location. The first and second communication networks 402 and 404 each include a plurality of network devices 406.

The data is transmitted by a transmitter 416 in the first communication network 402. The communication network 402 is shown here in a ring. It should be noted, however, that other network geometries are possible. In the ring-shaped structure of the first communication network 402, the transmitter 416 transmits the data to both its right and left neighbors in the ring structure.

Sending the data in two different directions should ensure two redundant transmission paths to the destination of the data. The data reaches both the coupling node 410 and the coupling node 412. Based on the source address of the sender, the data is forwarded from the coupling nodes 410 and 412 to the second communication network 404. Alternatively, such forwarding may be based on the destination address of the data. The decision as to whether data is forwarded to the second communication network 404 is made on the basis of the predefined information. The predefined information consists of a first and a second part. The first part is the source address of the data or the destination address of the data. The second part of the information is located in the coupling node. The second part of the information is read from a database.

After the data has been transferred from the coupling node 412 to the coupling node 414 and from the coupling node 410 to the coupling node 408, the data continues to be transmitted over two redundant transmission paths through the second communication network 404 transferred. A retransmission from the coupling nodes 408 and 414 to the coupling nodes 410 and 412 does not occur due to the predefined information.

The prevention of the retransmission of the data to the coupling nodes 410 and 412 may be determined by either the destination address or the source address of the data. For example, transmission from the second network 404 to the first network 402 is prevented when the source address in the databases of the coupling nodes 408 and 414 is connected to at least one FWC bit that prevents transmission to the first communication network 402. Alternatively, the transmission may be by designation bits - as in FIG. 3 described - prevented.

If the transmission by the FWC bits was prevented, the FWC bits 00 would be stored, for example, for the source address of the data in the coupling node 410, which allows a transmission into the second communication network 404. The FWC bits 00 are also stored in the database of the coupling node 412. In the coupling nodes 408 and 414 of the second communication network 404, the FWC bits 01 are connected to the source address of the data in the database. This prevents transmission to the first communication network 402.

In the prevention of data transmission by means of the destination address, as in FIG. 3 described, in the coupling node 410 and the coupling node 412, the transmission of the data to the second communication network 404 is allowed. In the coupling nodes 408 and 414, transmission of the data to the first communication network 402 is prevented.

Such a configuration of the coupling nodes is advantageous in order to prevent a retransmission of the data into the first communication network.

FIG. 5 is a schematic representation of a communication system 400 having a first communication network 402 and a second communication network 404.

The communication networks 402 and 404 are similar to those in FIG FIG. 4 built up. The transmitter 416 in turn transmits data to two network devices 406 of the first communication network 402. In the coupling nodes 410 and 412, data transmission into the second communication network 404 is prevented. The prevention can be done for example by FWC bits. For the source address of the transmitter 416, FWC bits 00 are stored for this purpose in the databases of the coupling nodes 410 and 412, which allow transmission of the data into the second communication network 404. However, for the source address of the transmitter 416 in the coupling nodes 408 and 414, the FWC bits 11 are stored, which do not allow a forwarding of the data within the second communication network 404. The data from the transmitter 416 are thus transmitted from the coupling node 410 to the coupling node 408 and from the coupling node 412 to the coupling node 414. However, the coupling nodes 408 and 414 do not transfer the data any further, thus avoiding unnecessary traffic in the second communication network 404.

Alternatively, the prevention of data transmission may be accomplished by comparing the destination address of the data with the database in the coupling nodes 408-414. In order to prevent data transmission from the first communication network 402 to the second communication network 404, it is defined in the received data link nodes 408 and 414 with this destination address in the database that such data is not forwarded via the ports connected to the second communication network 404. Thus, unnecessary data transfers in the second communication network 404 are prevented.

FIG. 6 FIG. 12 is a schematic view of a communication system 600 having a first communication network 402 and a second communication network 602. The communication network 602 is garland-shaped, so it does not form a self-contained ring. Again, it should be emphasized that other network geometries are applicable to the first and second communication networks 402 and 602. For ease of illustration, an annular first communication network 402 and a garland-shaped second communication network 602 are shown here.

In the second communication network 602 is the data transmitter 604, which transmits data to its two adjacent network devices 406. The data is forwarded via the coupling nodes 606 and 608 to the first communication network. A retransmission of the data into the second communication network 602 is prevented by the coupling nodes 606 and 608. The prevention can take place, for example, by storing the FWC bits 0: 1 for the source address of the data in the database of the coupling nodes 606 and 608, which makes possible a transmission of the data from the second communication network 602 into the first communication network 402. On the other hand, retransmission of the data from the first communication network 402 to the second communication network 602 is prevented by the FWC bits 0: 1.

Alternatively, in the databases, the coupling nodes 606 and 608 for the destination address of the data may be set with the setting bits so that these data may not be output through the port connected to the second communication network 602. Thus, a retransmission of the data from the first communication network 402 to the second communication network 602 is prevented.

FIG. 7 FIG. 12 is a schematic view of a communication system having a first communication network 402 and a second communication network 602. The two communication networks 402 and 602 are connected via the coupling nodes 606 and 608. In contrast to FIG. 6 is here now one Transmission of the data sent by the transmitter 604, the first communication network 402 to the second communication network 602 allows. This can be done, for example, by storing the forward control bits 0: 0 for the source address of the transmitter 604 in the coupling nodes 606 and 608 in the database, which allow the data to be transmitted back to the second communication network 602. Alternatively, for the destination address of the data may be determined by the determination bits in the database that a retransmission of the data in the second communication network 602 is possible. Thus, two redundant transmission paths are also created for a garland-shaped communication network such as the second communication network 602.

FIG. 8 FIG. 12 is a schematic view of a communication system 600 having a first communication network 402 and a second communication network 602. The data is transmitted by a transmitter 416 in the first communication network 402 in two directions. Coupling nodes 408 and 410 connect the first communication network 402 to the second communication network 602. When the data transmitted by the transmitter 416 reaches the coupling nodes 408 and 410, the data is forwarded to network devices 406 of the second communication network 602. A retransmission of the data from the second communication network 602 to the first communication network 402 is prevented.

The prevention can be done for example by forward control bits. For this purpose, the forward control bits 10 are stored in the databases of the coupling nodes 408 and 410 for the source address of the transmitter 416. These forward control bits prevent the data from being transferred back from the second communication network 602 to the first communication network 402.

Alternatively, the prevention of the retransmission of the data from the second communication network 602 to the first communication network 402 by the commit bits. For this purpose, in the databases, the coupling nodes 408 and 410 for the destination address of the data 416 are not assigned any transmission ports upon receipt via the ports connected to the second communication network 602. Thus, transmission of the data from the second communication network 602 to the first communication network 402 is prevented.

FIG. 9 Figure 10 is a block diagram of a coupling node 900. The coupling node 900 includes a plurality of ports 902. Each port 902 is suitable for receiving and transmitting data. In addition, the coupling node 900 comprises a digital storage medium 904. On the digital storage medium 904, the database is stored with the second part of the predefined information. In addition, a program of instructions is stored with the digital storage medium 904. The program may be executed by the processor 906 of the coupling node 900. Upon execution of the program, the receiving port is registered when receiving data and the first part of the predefined information is read from the data. The first part of the predefined information is compared with the database of the coupling node 900 and the second part of the predefined information is read out. The processor 906 is adapted to prevent, upon execution of the program, the retransmission of data originally received from the first communication network and received by the second communication network back into the first communication network.

LIST OF REFERENCE NUMBERS

100

Database entry

102

source address

104

FWC bits

200

coupling node

202

port

204

port

206

port

208

port

300

Database entry

302

destination address

304

Fixing bits

306

Fixing bits

308

Fixing bits

310

Fixing bits

400

communication system

402

Communication network

404

Communication network

406

Network device

408

coupling node

410

coupling node

412

coupling node

414

coupling node

416

transmitter

600

communication system

602

Communication network

604

transmitter

606

coupling node

608

coupling node

900

coupling node

902

port

904

storage medium

906

processor

Claims (12)

1. Method for redundant communication in a communication system (400; 600),
   wherein the communication system comprises a number of communication networks (402; 404; 602),
   wherein the communication networks are connected to each other via at least one node (408; 410; 412; 414; 606; 608; 900),
   wherein the communication networks comprise a number of network devices (406),
   wherein the method comprises the following steps:

   - Transmission of data from the first network device (416; 604) of the first communication network to a second network device of the second communication network via at least one node and/or from the first network device to a third network device of the first communication network, wherein transmission from the first to the second network device and/or transmission from the first to the third network device is undertaken via at least two redundant transmission paths,
   characterised by

   - Prevention of the data being transmitted back from the second to the first communication network during a transmission from the first to the second network device based on information predefined before the transmission, wherein the predefined information consists of a first part and a second part (100; 300), wherein the data comprises the first part of the predefined information and wherein the node comprises the second part of the predefined information.
2. Method in accordance with claim 1, wherein the first part of the predefined information is read from the at least one node.
3. Method in accordance with claim 2, wherein the node comprises a number of ports (202; 204; 206; 208; 902; 904), with data being able to be received and sent by each of the ports, wherein the second part of the predefined information is located in a database, with the database comprising a number of entries (100),
   wherein the method further comprises the following steps:

   - Receipt of data at a first port,

   - Reading out of the first part of the predefined information,

   - Determination of the second part (104) of the predefined information by comparing the database entries with the first part of the predefined information,

   - Reading out of the least one second port for forwarding the data from the second part of the predefined information if the second part of the predefined information comprises at least one second port,

   - Forwarding the data via the least one second port if the second part of the predefined information includes at least one second port,

   - Preventing forwarding of the data if the second part of the predefined information does not include a second port.
4. Method in accordance with one of claims 1 or 2, wherein the node includes a number of ports, wherein data is able to be received and sent by each of the ports, wherein the second part of the predefined information is located in a database, wherein the database includes a number of entries, wherein each entry includes for each of the ports no or at least one associated send port, wherein the first part of the predefined information includes a data destination,
   wherein the method further comprises the following steps:

   - Receipt of the data at a first port,

   - Reading out of the data destination and registration of the first port,

   - Searching in the database for a database entry (300) matching the data destination and the first port,

   - Reading out from the database the at least one send port (304; 306; 308; 310) belonging to the first port if the database entry includes at least one send port,

   - Forwarding of the data about the at least one read-out send port if the database entry includes at least one send port,

   - Preventing forwarding of the data if the database entry does not include a send port.
5. Method in accordance with claim 4, wherein each database entry and the data destination are characterized by a multicast address or a unicast address.
6. Method in accordance with one of the preceding claims, wherein the communication system is an automation system and wherein the data is automation data.
7. Node (200; 408; 410; 412; 414; 606; 608; 900) with a number of ports (202; 204; 206; 208; 902), wherein the ports are embodied to connect at least one first communication network (402) of a communication system (400) to a second communication network (404; 602) of the communication system, wherein data is able to be received via the ports from the first and the second communication networks and able to be sent out to the first and the second communication networks, wherein the node includes means (906) for reading out a first part of predefined information from the data,
   characterised in that

   - the node includes storage means (906) and read-out means (906) for storing and reading out a second part of the predefined information,

   - the node includes prevention means (906),

   - the prevention means are embodied, depending on the predefined information, for preventing a transmission of received data that originates from the first communication network and is received at the node from the second communication network, back into the first communication network
8. Node in accordance with claim 7, wherein the node is embodied for executing a method in accordance with one of claims 1 to 6.
9. Computer-readable storage medium (904) with instructions which, when executed in a node in accordance with one of claims 7 or 8 in a communication system, cause the node to carry out the following method:

   - Receipt of data via a first port,

   - Registration of the first port,

   - Reading out a first part of predefined information from the received data,

   - Reading out a second part of the predefined information from storage means of the node,

   - Preventing the received data that originates from the first communication network and has been received at the node from the second communication network, from being transmitted back into the first communication network on the basis of the predefined information.
10. Computer-readable storage medium in accordance with claim 9, wherein the computer-readable storage medium is embodied for carrying out a method in accordance with one of claims 1 to 7.
11. A communication system (400) with a node (200; 408; 410; 412; 414) in accordance with one of claims 7 or 8, wherein the communication system includes at least a first (402) and a second communication network (404; 602), wherein the node includes a number of ports (202; 204; 206; 208; 902), wherein the node connects at least the first communication network to the second communication network of the communication system via the ports.
12. Communication system in accordance with claim 11, wherein the communication system is embodied for carrying out a method in accordance with one of claims 1 to 6.

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